Thermoplastic moulding compositions on the basis of saturated polyesters

ABSTRACT

Thermoplastic moulding compositions on the basis of linear saturated polyesters wherein the polyester granules containing a neutral or partially neutralized salt of montan wax or of montan wax esters is additionally coated with a neutral or partially neutralized salt of montan wax or of montan wax esters.

United States Patent Klaus Weissermel Kelkheim /Taunus;

Rudolf Kern, Mainz; Heinz Schmidt, Frankfurt am Main; Walter Herwig,Frankfurt am Main, all of Germany 8 1 7,550

Apr. 18, 1969 Nov. 9, 197 1 Farbwerke Hoechst Aktiengesellschaft vormalsMeister Lucius & Bruning Frankfurt am Main, Germany Dec. 12, 1968Germany Inventors Appl. No. Filed Patented Assignee PriorityTHERMOPLASTIC MOULDING COMPOSITIONS ON THE BASIS OF SATURATED POLYESTERS15 Claims, No Drawings 168,138.8 F, 121; 260/37 EP, 835, 28

I 56] References Cited UNITED STATES PATENTS 2779.745 1/1957 Howland117/100 X 2,962 469 11/1960 Phillips et al. .1 260/835 3,180,750 4/1965Shipee etal 260/28 3,193,601 7/1965 Billingsley 264/142 3,245,817 4/1966Lovness 117/168 3 405,102 10/1968 Kugler et al. 260/37 3,461,088 8/1969Stahnecker et a1. 117/100 3,461,092 8/1969 Sory 117/100 FOREIGN PATENTS847,059 9/1960 Great Britain 1 17/100 Primary Examiner-William D. MartinAssistant Examiner--- Mathew R. P. Perrone, Jr. A110rneyCurtis, Morrisand SatTord ABSTRACT: Thermoplastic moulding compositions on the basisof linear saturated polyesters wherein the polyester granules containinga neutral or partially neutralized salt 01' montan wax or of montan waxesters is additionally coated with a neutral or partially neutralizedsalt of montan wax or of montan wax esters.

THERMOPLASTIC MOULDING COMPOSITIONS ON THE BASIS OF SATURATED POLYESTERSThe present invention relates to thermoplastic moulding compositions onthe basis of saturated polyesters, which moulding compositions haveimproved properties.

It has been proposed to produce shaped articles from thermoplasticmoulding compositions comprising saturated linear polyesters of aromaticdicarboxylic acids. It has also been proposed to add to polyethyleneterephthalate finely divided inorganic substances as nucleating agentsto increase the speed of crystallization of the injection mouldedpolyester in the mould. By this step the crystallinity and the densityof the injection moulded articles are increased and therewith thedimensional stability and stability of shape at elevated temperature areimproved. As solid inorganic substances there have been proposed, forexample, metal oxides, alkaline earth metal salts, talc powder, glasspowder, or metals. The inorganic substances should have a particle sizeof less than 2 microns.

it has likewise been proposed further to increase the speed ofcrystallization by adding to the polyesters a mixture of the inorganicnucleating agents with specific epoxides.

In copending Application Ser. No. 817,545 filed concurrently herewith aprocess for the manufacture of rapidly crystallizing mouldingcompositions on the basis of saturated linear polyesters is described inwhich the polyester mixed with inert inorganic solids and specificepoxides is coated, after the usual after-condensation, with a salt of amontan wax or of a montan wax ester.

By the addition of montan wax salts or salts of montan wax esters to thepolyester composition containing inorganic nucleating agents andspecific epoxides, the injection cycle can be considerably shortened andtherewith the rate of production increased without the utilitarianproperties of the polyester being detrimentally affected.

Further experiments have revealed that the aforesaid process can befurther simplified.

It has now been found that thermoplastic moulding compositions on thebasis of saturated linear polyesters and having advantageous propertiescan be produced by coating polyester granules containing 0.05 to 1.5percent by weight, preferably 0.1 to 1 percent by weight, and morepreferably 0.15 to 0.6 percent by weight, calculated on the polyester,of neutral or partially neutralized salts of montan wax or of montan waxesters, optionally together with other known additives, which polyestergranules have a reduced specific viscosity of at least 1.25 dl./g.,measured with a 1 percent solution in a 60:40 mixture of phenol andtetrachloroethane at 25 C., and a moisture content of less than 0.01percent by weight, with 0.01 to 1 percent by weight, preferably 0.05 to0.5 percent by weight, and more preferably 0.1 to 0.4 percent by weight,calculated on the polyester, of neutral or partially neutralized salts'of montan wax or of esters of montan wax.

As compared with the process proposed in our copending applicationreferred to above, the present process offers various advantages.

Montanates are better compatible with the polyester than the inorganicsolids. As the salts of montan wax melt during processing, they are morefinely divided in the polyester and more effective than the inorganicsolids. Moreover, the formation of agglomerates, which may occur withthe sole addition of inorganic solids and cause flaws whereby the impactstrength of the moulded articles is reduced, is not observed.

As polyester polyethylene terephthalate is used in the first place.Other suitable polyesters are, for example, polycyclohexane-l,4-dimethylol terephthalate or polyesters containing as acid component,in addition to terephthalic acid, up to 5 mole percent of other aromaticor aliphatic dicarboxylic acids, such as isophthalic acid,naphthalene-2, 6 -dicarboxylic acid or adipic acid, or as alcoholiccomponent, in addition to ethylene glycol, up to 30 mole percent ofother aliphatic diols, such as 2, 2-dirnethylpropane-diol(l, 3) orbutane-diol-(l, 4), or up to l percent of tetrols, for example l,l,4,4-tetramethylolcyclohexane. Polyesters of hydroxy-carboxylic acids mayalso be used. The polyesters should have a reduced specific viscosityoffrom 0.6 to 2.0 d1./g., preferably 0.9 to 1.6 dl./g., measured with a1 percent polymer solution in a 60:40 mixture of phenol andtetrachloroethane at 25 C. Especially good results are obtained withpolyesters having a reduced specific viscosity of from 1.1 to 1.5 d1./g.Prior to coating with the salts of montan wax or esters of montan waxthe polyesters should have a reduced specific viscosity of at least 1.25d1./g. If necessary, this value can be reached by subjecting thepolyester to an after-condensation.

Montan acid is an acid mixture essentially consisting of aliphaticmonocarboxylic acids having 26 to 32 carbon atoms in the chain. Suitablesalts of montan wax contain as cation metals of main groups 1-I11 of thePeriodic System, preferably Li, Na, K, Be, mg. Ca, and Al, sodiummontanates being preferred. As partially neutralized salts of montan waxthere are used salts obtained by reacting montan acid with 0.1 to 1equivalent of alkali metal hydroxide or alkali metal oxide, preferablysalts obtained with 0.25 to 0.9 equivalent of sodium hydroxide.

Salts of montan wax esters that can be used are obtained by partialesterification of montan acids with up to 0.90 equivalent, preferably0.5 to 0.8 equivalent of dihydric alcohols having 2 to 4 carbon atoms inthe alkylene group, with subsequent neutralization with oxides orhydroxides of the metals specified above. Especially suitable diols are,for example, ethylene glycol, 1, 2-propane-diol, 1,3-propane-diol, l, 3-butane-dio] and l, 4 -butane-diol.

The salts of montan wax or of esters of montan wax acting as nucleatingagents can be added to the finished polyester granules or during themanufacture of the polyester prior to or during polycondensation.Optionally, other known additives may also be added. The coated granulesare homogenized, for example in an extruder, and then granulated again.

Known additives are, for example inorganic nucleating agents, such asalkaline earth metal carbonates, for example calcium magnesiumcarbonate, and oxides such as titanium oxide or aluminum oxide, as wellas talc and aluminum silicates, preferably sodium-aluminum silicate.

The inorganic nucleating agents are added to the polyester in an amountin the range of from 0 to 2 percent by weight, preferably 0 to 0.6percent by weight, calculated on the polyester.

Further known additives are polyfunctional epoxides of the generalformula Rr 0 R3 in which R, R R and R stand for hydrogen, alkyl,cycloalkyl, aryl or aralkyl groups, which may be linked to one anotherwith formation of ring structures and may contain ether or estergroupings. In general, the specified epoxides are added also in anamount in the range of from 0 to 2 percent by weight, preferably 0 to0.3 percent by weight, calculated on the polyester. Suitablepolyfunctional epoxides are, for example, alkylene-polyol-glycidylethers or butanediol-( l, 4) diglycidyl ether.

By coating the polyester granules with a salt of a montan wax or amontan wax ester there is obtained not only a rapid crystallization ofthe moulded article in the mould and better mould release properties,but simultaneously the granules are protected against the absorption ofmoisture. To obtain unobjectionable injection moulded articles thepolyester moulding composition should contain as little moisture aspossible, preferably less than 0.01 percent by weight.

In order to bring about crystallization in the mould the mould must bemaintained at a temperature of at least 1 10 C. A rapid crystallizationand therewith short injection cycles are obtained with mouldtemperatures in the range of from to 150 C., preferably offrom to 154 C.

Tests were carried out using the injection mould for a program controldial of a washing machine wherein the dial was pressed out of the mouldby very sharp ejector pins. The injection cycle was defined after whichthe ejector pins did just not penetrate into the finished mouldedarticles and the article fell from the mould almost by itself.

The following examples serve to illustrate the invention but they arenot intended to limit it thereto, the percentages are percent by weight,calculated on the polyethylene terephthalate.

EXAMPLE 1 Granules of polyethylene terephthalate having a moisturecontent below 0.01 percent and a reduced specific viscosity of 1.40oil/g. were rolled for 1 hour with 0.4 percent of sodium montanate. Thecoated granules were homogenized in an extruder at a temperature of 275C., the melt was extruded into water in the form of a wire andgranulated. Next, the granules were dried until the moisture content haddropped below 0.01 percent and the reduced specific viscosity was raisedto 1.40 dl./g. by heating the granules for 7-8 hours at 240 C. under apressure of 0.4 mm. of mercury. Finally, the granules were coated with0.2 percent of sodium montanate.

With the granules obtained program control dials having a diameter of 10cm. were injection moulded at a cylinder temperature of 265 C. and atemperature of the mould of 140 C. The total injection cycle was 60seconds. The residence time in the mould was chosen in such a mannerthat the ejector pins did no longer penetrate into the moulded articleswhen the mould was opened. The moulded articles had excellent surfaceproperties were free from flashes and had a density of 1.370 g./cc.

The impact strength of the injection moulded articles was determinedwith the drop hammer tester in the manner described below. The height atwhich 50 percent of the samples broke was 2.00 meters.

Drop hammer tester:

A sheet of 70 70X4 mm. is pneumatically clamped on a table and thedropping hammer 1 kg) is suspended on a stop device with which it isascended to the desired height. The dropping hammer is releasedpneumatically and hits the sample in the center of the clamping ring.When the samples is not punched the dropping hammer is held by apneumatically operated receiver when it jumps back. 10 Sheets are testedfor each height and the height is determined at which 50 percent of thesheets break 50 percent breaking limit.

COMPARATIVE EXAMPLE 1 Granules of polyethylene terephthalate having amoisture content of less than 0.01 percent and a reduced specificviscosity of 1.40 dl./g. measured with a 1 percent solution in a 60:40mixture of phenol and tetrachloroethane at 25 C., were rolled for 1 hourtogether with 0.6 percent of sodium montanate. The coated granules werehomogenized in an extruder at a temperature of 275 C., the melt wasextruded in wire form into water and granulated. The moisture content ofthe granules was again reduced to a value below 0.01 percent by weightand the reduced specific viscosity was raised to 1.4 dl./g. by heatingthe granules for 6 to 8 hours at 240 C. under a pressure f0.4 mm. ofmercury.

With the granules program control dials having a diameter of about 10cm. were injection moulded at a cylinder temperature of 265 C. and atemperature of the mould of 140 C. The total injection cycle lasted formore than 90 seconds. Even with the long residence time in the mould theejector pins penetrated considerably into the moulded article which wastacky and difficult to remove from the mould. The injection mouldedarticles were strongly distorted. The density was found to be 1.370g./cc.

EXAMPLE 2 Granules of polyethylene terephthalate having a moisturecontent of less than 0.01 percent and a reduced specific viscosity of1.40 dl./g. were rolled for 1 hour together with 0.2 percent ofsodium-aluminum silicate and 0.2 percent of sodium montanate. The coatedgranules were homogenized in an extruder at 275 C., the melt wasextruded into water in the form of a wire and granulated. The granuleswere then dried until the moisture content had dropped below 0.01percent and heated for 7 to 8 hours until the reduced specific viscositywas 1.4 dl./g. Finally, the granules were coated with 0.2 percent ofsodium montanate.

With the granules obtained program control dials having a diameter of 10cm were injection moulded at a cylinder temperature of 265 C. and atemperature of the mould of 140 C. The total injection cycle was 75seconds. The residence time in the mould was chosen in such a mannerthat the ejector pins did not penetrate into the articles when the mouldwas opened. The moulded articles had excellent surface properties, werefree from flashes and had a density of 1.370 g./cc.

In the drop hammer test the 50 percent breaking limit was 2.00 m.

EXAMPLE 3 Granules of polyethylene terephthalate having a moisturecontent of less than 0.01 percent and a reduced specific viscosity of1.40 dl./g. were rolled for 1 hour together with 0.4 percent of montanacid partially neutralized with 0.80 equivalent NaOl-l. The coatedgranules were homogenized in an extruder at a temperature of 275 C., themelt was extruded into water in the form of a wire and granulated.

The granules were then dried until the moisture content had droppedbelow 0.01 percent and the reduced specific viscosity was raised to 1.4dL/g. by heating the granules for 7 to 8 hours at 240 C. under apressure of 0.4 mm. of mercury. Finally the granules were coated with0.3 percent of montan acid which had been partially neutralized with0.80 equivalent NaOH.

With the granules program control dials having a diameter of 10 cm. wereinjection moulded at a cylinder temperature of 265 C. and a temperatureof the mould of 140 C. The total injection cycle was seconds. Theresidence time in the mould was chosen in such a manner that the ejectorpins did no longer penetrate into the articles when the mould wasopened. The injection moulded articles had excellent surface properties,they were free from flashes and had a density of 1.369 gJcc.

In the drop hammer test the height at which 50 percent of the sheetsbroke was 1.80 in.

EXAMPLE 4 Granules of polyethylene terephthalate having a moisturecontent of less than 0.01 percent and a reduced specific viscosity of1.40 dl./g. were rolled for 1 hour together with 0.2 percent ofbutane-diol-l,4-diglycidyl ether and 0.5 percent of a montan acidpartially neutralized with 0.70 equivalent NaOH and partially esterifiedwith 0.30 equivalent ethylene glycol. The coated granules werehomogenized in an extruder at a temperature of 275 C., the melt wasextruded into water in the form of a wire and granulated. The granuleswere than dried until the moisture content had dropped below 0.01percent and the specific viscosity was raised to 1.40 dL/g. by heatingthe granules for 7 to 8 hours at 240 C. under a pressure of 0.4 mm. ofmercury. The granules were then coated with 0.2 percent of montan acidwhich had been partially neutralized with 0.70 equivalent NaOH andpartially esterified with 0.30 equivalent ethylene glycol.

With the granules program control dials having a diameter of 10 cm. wereinjection moulded at a cylinder temperature of 265 C. and a temperatureof the mould of C. The total injection cycle was 75 seconds. Theresidence time in the mould was chosen in such a manner that the ejectorpins did no longer penetrate into the articles when the mould wasopened. The injection moulded articles had excellent surface properties,they were free from flashes and had a density of 1.370 g./cc.

We claim:

1. A composition consisting essentially of granules of a saturatedlinear polyester of terephthalic acid and a saturated aliphatic orcycloaliphatic diol containing 0.05 to 1.5 percent by weight, calculatedon the weight of the polyester, of a neutral or partially neutralizedsalt of montan wax or montan wax ester, said granules having a reducedspecific viscosity of at least L25 dL/g. measured in a l percentsolution in a 60:40 mixture of phenol and tetrachlorethane at 25 C., andhaving a moisture content of less than 0.0l percent by weight, saidgranules being coated with 0.01 to l percent by weight, calculated onthe weight of the polyester, of a neutral or partially neutralized saltof montan wax or montan wax ester.

2. The composition of claim 1, wherein the polyester granules containother additives in addition to the neutral or partially neutralized saltof montan wax or of montan wax ester.

3. The composition of claim I, wherein the saturated linear polyester ispolyethylene terephthalate.

4. The composition of claim 1, wherein the saturated linear polyester ispolycyclohexane-1,4-dimethylol terephthalate.

5. The composition of claim 3, wherein the linear saturated polyestercontains as acid component, in addition to terephthalic acid, up to 5mole percent of another aromatic or aliphatic dicarboxylic acid.

6. The composition of claim 3, wherein the polyester contains as diolcomponent, in addition to ethylene glycol, up to 30 mole percent ofanother aliphatic diol.

7. The composition of claim 5, wherein the polyester contains as acidcomponent a hydroxycarboxylic acid.

8. The composition of claim 1, wherein a neutral or partiallyneutralized salt of a metal of main groups I to ill of the PeriodicTable is used.

9. The composition of claim 8, wherein the salt is sodium montanate.

10. The composition of claim 1, wherein the salt of montan acidneutralized with 0.1 to 1 equivalent of alkali metal hydroxide or oxideis used.

11. The composition of claim 2, wherein the additives are inorganicnucleating agents selected from the group consisting of alkaline earthmetal carbonates, titanium dioxide, aluminum oxide, talc, aluminumsilicates and sodium-aluminum silicate.

12. The composition of claim 11, wherein the inorganic nucleating agentis added in an amount of up to 2 percent by weight, calculated on theweight of the polyester.

13. The composition of claim 2, wherein the additive is a polyfunctionalepoxide of the general formula

2. The composition of claim 1, wherein the polyester granules containother additives in addition to the neutral or partially neutralized saltof montan wax or of montan wax ester.
 3. The composition of claim 1,wherein the saturated linear polyester is polyethylene terephthalate. 4.The composition of claim 1, wherein the saturated linear polyester ispolycyclohexane-1,4-dimethylol terephthalate.
 5. The composition ofclaim 3, wherein the linear saturated polyester contains as acidcomponent, in addition to terephthalic acid, up to 5 mole percent ofanother aromatic or aliphatic dicarboxylic acid.
 6. The composition ofclaim 3, wherein the polyester contains as diol component, in additionto ethylene glycol, up to 30 mole percent of anotHer aliphatic diol. 7.The composition of claim 5, wherein the polyester contains as acidcomponent a hydroxycarboxylic acid.
 8. The composition of claim 1,wherein a neutral or partially neutralized salt of a metal of maingroups I to III of the Periodic Table is used.
 9. The composition ofclaim 8, wherein the salt is sodium montanate.
 10. The composition ofclaim 1, wherein the salt of montan acid neutralized with 0.1 to 1equivalent of alkali metal hydroxide or oxide is used.
 11. Thecomposition of claim 2, wherein the additives are inorganic nucleatingagents selected from the group consisting of alkaline earth metalcarbonates, titanium dioxide, aluminum oxide, talc, aluminum silicatesand sodium-aluminum silicate.
 12. The composition of claim 11, whereinthe inorganic nucleating agent is added in an amount of up to 2 percentby weight, calculated on the weight of the polyester.
 13. Thecomposition of claim 2, wherein the additive is a polyfunctional epoxideof the general formula
 14. The composition of claim 13, wherein thepolyfunctional epoxide is selected from the group consisting ofalkylene-polyol glycidyl ethers and butane-diol-1,4-diglycidyl ether.15. The composition of claim 13, wherein the epoxide is added in anamount of up to 2 percent by weight, calculated on the weight of thepolyester.